LOVE LOVE LOVE minis! I got into the hobby when I was 10 and was over at a friend's house whose older brother played D&D, and he had some old Ral Partha minis. They were painted like crap, but I still thought they were so cool- and it made me really want to play the game that used them.
Ever since I started gaming in 1983, I've used them. For me, they really spark my imagination and get me into the game- but in a kind of unusual way. You see, when I paint minis is when I come up with my best gaming stuff- usually from a DM's point of view, but ideas for PCs pop into my head too. I'm not sure why this is- maybe because I'm so focused when painting that my brain is on overdrive, and not thinking about my lectures or work in lab, that I have more attentional resources to devote to really consider gaming- I'm not entirely sure.
Mostly, I prefer lead/pewter minis. I have probably 10,000 minis stowed in totes, foam-padded boxes, etc. To me, the pewter minis are a lot more detailed and fun to play with, but I do occasionally buy pre-painted plastic minis if its something I can't get in pewter (like a devourer for example) and repaint it.
When I hear people say they hate using minis because it kills their imagination, I have to wonder what the disconnect is. Now, I've been in groups where the DM just set minis on the table and started a fight with almost no evocative description- and that does ruin the fun for me. I suspect people who really hate minis might hate them for this reason- the DM got lazy and just runs a series of battles. When I DM, I try to imagine the location or situation in my head first, then describe it in detail to the PCs....and only then do I whip out minis and draw the area on a battlemat if combat is going to happen.
I really don't understand the mutual exclusivity some people believe in when it comes to minis and role-playing- thats never been a problem for me or my group, but maybe someone can explain it to me.